Monitoring Resource Limit

When issues arising regarding oracle database from software development team or client side then at first we need to focus on the view V_$RESOURCE_LIMIT.

Like someone from your premises said no more connection can't be made from sql developer or toad.

Then you tune 

select RESOURCE_NAME,CURRENT_UTILIZATION,MAX_UTILIZATION,INITIAL_ALLOCATION from V$RESOURCE_LIMIT where RESOURCE_NAME= 'processes';

Suppose saw that CURRENT_UTILIZATION of processes resource has been used which defined on INITIAL_ALLOCATION.

A professional dba can take decision from this scenario. 

Decision: INITIAL_ALLOCATION of processes resource need to be increased.

Treatment: 

determine the current limit value 

sqlplus / as sysdba

show parameter processes;

set the new value for maximum processes greater than or equal 250 depending on the database option you offer.

alter system set processes=250 scope=spfile;

reference:

https://docs.oracle.com/cd/E29633_01/CDMIG/GUID-06C3ACB1-B48C-49E9-830A-B1F3B84B3DA7.htm